One of the primary technical challenges associated with the manufacture of optical systems, and especially systems offering higher levels of integration, is component alignment. This thesis is especially applicable in free-space-interconnect optical systems where optical components, such as active device (e.g., semiconductor lasers), passive devices (e.g., filters), and/or MOEMS (micro-optical electromechanical systems) (e.g., tunable filters and switches) are integrated together on a common submount or micro-optical bench. Scales characteristic of such optical components can necessitate sub-ten micrometer to sub-micrometer alignment accuracy.
There are two general classes of alignment strategies: active and passive. Typically, in passive alignment of the optical components, registration or alignment features are fabricated directly on the components as well as on the platform to which the components are to be mounted. The components are then mounted and bonded directly to the platform using the alignment features. In active alignment, an optical signal is transmitted through the components and detected, sometimes after an initial passive alignment of the components. The alignment is performed based on the transmission characteristics to en able the highest possible performance level for the system.
Generally, optical system manufacturing systems seek to improve the speed at which the optical systems can be manufactured using passive alignment. In the ideal case, the optical systems can be manufactured using all passive alignment strategies, but even if an all-passive alignment approach is not possible requiring a subsequent active alignment xe2x80x9ctuning or optimization stepxe2x80x9d, the precision of the passive alignment is critical to minimizing the time required in the final active alignment.
The present invention concerns a structure that is compatible with passive alignment. Specifically, an alignment system is described that is capable of integration onto a micro-optical bench system, provides for the secure attachment of optical components to the bench, and yields component installation in a known and reproducible fashion.
In general, according to one aspect, the invention concerns an optical bench system. The system comprises a base and a clip structure for an optical component that is formed in the base.
According to the preferred embodiment, the clip structure is etched into bulk material of the base. In one implementation, the clip structure is created using reactive ion etching in silicon or silicon-on-insulator (SOI) wafer material. Alternatively, other material systems, such as those based on III-V material systems can be used along with other anisotropic etching techniques such as those based on crystallographic orientation. Further, electroforming techniques can be used such as those provided by the LIGA process.
In the preferred embodiment, the clip comprises an alignment wall and a resilient arm. The resilient arm engages a first side of the optical component to urge a second side of the optical component into engagement with the alignment wall. This cooperation between the arm and the alignment wall allows for precise registration of the optical component against the alignment wall and a secure engagement to yield alignment accuracies equivalent to that attainable with semiconductor lithography processes.
In order to ease installation of the optical component into the structure, an insertion channel may further be provided. Specifically, the optical component is inserted into the base or bench via the insertion channel and then slide into engagement between the resilient arm and the alignment wall. Specifically, a wall of the insertion channel smoothly transitions into the alignment wall. An opposed side of the insertion channel is formed by a base region of the arm.
In order to provide for further registration of the optical component in the clip structure, cooperating bench and component registration features are preferably provided. Typically, a bench registration feature engages a component registration feature to locate the optical component in a longitudinal direction to the clip structure.
Further, vertical registration features can be provided between the optical component and the bench to register the optical component in a vertical direction relative to the plane of the bench. In one embodiment, a projecting stub is provided on the optical component that engages the bench when the optical component has been fully inserted into the clip structure.
One further feature is to provided an electrode and trace on the optical bench, which the stub engages to provide for electrical connection to the optical component. A permanent mechanical connection between the stub and the electrode can be provided by a subsequent solder reflow step.
The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.